1. Field of the Invention
This invention has relation to wheel mounted field sprayers for application of liquid agricultural chemicals to the ground through a plurality of transversely spaced-apart nozzles, and more specifically to the monitoring of flow and the detection of the absence of liquid flow through each individual nozzle.
2. Description of the Prior Art
It is known to spray agricultural chemicals through a plurality of spaced-apart nozzles as tractors or other prime movers propel spray booms over the ground. See U.S. Pat. No. 3,425,628 granted to Reams on Feb. 4, 1969, and U.S. Pat. No. 4,553,702 granted to Coffee et al. on Nov. 19, 1985.
The patent to Coffee et al. shows liquid detectors between the storage tanks and the boom and are for the purpose of sensing as to whether or not a particular chemical is being added to the mixture. In that patent are disclosed liquid detection devices 216 and 217 which merely report the presence or absence of liquid in a conduit. They cannot determine whether there is flow through the conduit. Further, there is no suggestion of the use of a trapped "air bubble" to deprive electrodes of contact with liquid whenever there is no flow of liquid in a conduit.
U.S. Pat. No. 4,430,886 granted to Rood on Feb. 14, 1984, shows the use of a reduction in pressure drop between an upstream restrictor and a downstream ON-OFF valve to indicate a partially closed nozzle. Rather than detect the presence or absence of flow in one of a multiplicity of nozzles, this invention measures the pressure in one nozzle.
U.S. Pat. No. 2,869,368 granted to Brown on Jan. 20, 1959, senses the presence of a liquid at various levels in the tank by using a multiplicity of vertically spaced electrodes. The patent is not concerned with the flow of liquid through a conduit or a tank, but is concerned merely with establishing the level of liquid existing in the tank at a particular point in time.
U.S. Pat. No. 4,115,877 granted to Wall on Sept. 26, 1978, shows the use of an electrode which can be submerged into a liquid in a U-tube. The change in capacitance between the electrode and a side wall surrounding the electrode indicates the liquid level in the tube. The patent is not concerned with the monitoring of flow and the signalling of lack of flow in each one of a multiplicity of tubes or conduits.
U.S. Pat. No. 4,777,832 granted to Prodosmo et al. on Oct. 18, 1988, is also concerned with indicating a level of a liquid in a vessel, using the presence of water in a U-tube. It is not related to detecting and indicating flow and lack of flow in a tube.
U.S. Pat. No. 4,182,363 granted to Fuller on Jan. 8, 1980, shows the use of electrodes at various heights to indicate and control the height of liquid in a reservoir. It does not detect, and cannot detect, the presence and absence of flow in a tube.
U.S. Pat. No. 4,052,003 granted to Steffen on Oct. 4, 1977, discloses a pressure sensor developing an electrical signal related to the pressure in a spray bar. This monitoring of the total pressure supplied to all nozzles does not show or suggest how to detect the cessation of flow in any individual nozzle. The concept of using an air bubble to detect and indicate flow and lack of flow is not shown or suggested.
U.S. Pat. No. 4,530,465 granted to Gauchet et al. on July 23, 1985, shows a flow rate sensor which regulates pressure of liquid being delivered to all of the spray heads. This is done by measuring the time required for emptying a predetermined volume of fluid (column 3, lines 1-3 and column 5, lines 31-33). There are no means here of indicating stoppage of flow to individual spray heads.
The foregoing patents were uncovered in a preliminary search made in the records of the United States Patent and Trademark Office.
There are mechanical devices used for the same purpose, some of which are believed to be spring operated for example. The details of these are unknown to the inventor and those in privity with him. It is believed that these are very complicated and/or expensive compared to the device of the present invention, and they have not found favor in the marketplace.
The present inventor experimented earlier with infra-red emitters and detectors in an attempt to monitor and detect cessation of flow to individual nozzles, but abandoned any attempt to use optical sensors because of the problem of finding a remote location to monitor each nozzle. Also, because of the environment in which such detectors must work, the ends of the light fibers or glass lenses collect dust, spray mist and suspended agricultural powders, become dirty and, therefore, rapidly become inoperative.
The inventor and those in privity with him are aware of no prior art closer than that discussed above; and are aware of no prior art or combination thereof which anticipates the claims herein.